maybe not software but you can restore your phone back from an earlier date which will bring the pictures back but every change since then will get cleared as well unless you create a backup before restoring it. long process but its the only was i can see you getting them back

According to Apple, the photos get backed up in iTunes when you do a sync/backup, so connect your phone to iTunes and restore from the latest backup.
It's not a good idea to store photos in the camera roll of your phone.

Quote:

"Camera Roll (Photos, screenshots, images saved, and videos taken. Videos greater than 2 GB are backed up with iOS 4.0 and later.)
Note: For devices without a camera, Camera Roll is called Saved Photos."

So I did backup my phone using iTunes. If I restore from that backup, will I be able to get back some pictures that have been deleted since then? When I select Restore from Backup in iTunes, it says it will only restore contacts, calendars, text messages, and settings...nothing about photos.

Aren't the photos saved in the iTunes backup? It may not have all of them, but when you back up your phone I think if you restore from a previous backup then you could possibly retrive them. I may be wrong, but I read somewhere a long time ago that it was an option. Have you ever backed up; not sync'd but backed up?
Once you do that, grab those photos (if it works) and then restore from the latest backup.